Referring to FIGS. 1 and 3, the assembled perspective view and the exploded view of the conventional male stud 24 are illustrated. The prior art includes a suction cylinder 1 which is a long pump, a frame-like handle 2 connected to a rear end of the suction cylinder 1; and a pull 3 which is formed by a transversal pull rod 31 passing through the suction cylinder 1. A T shape pull handle 32 is connected to a rear end of the pull rod 31. A piston 4 is installed in the suction cylinder 1 and is fixed to a font end of the pull rod 31. An expandable spring 5 is serially connected to the pull rod 31 and a front end thereof resists against the piston 4 and a rear end thereof resists against the frame like handle.
A front end of the suction cylinder 1 is an air opening, and a rear end thereof is screwed into a female screw 23 by a male thread 12. An outer edge of the pull rod 31 of the pull 3 is installed with a plurality of protruded guides 33. The guides 33 of the pull 31 pass through the through hole 21 and guide recesses 22 of the handle 2. A front end of the pull rod 31 is firmly secured to the screw hole 44 of the piston 4 by a connected screw rod 34. The piston 4 is formed by an annular front guide 41, an annular rear guide 42 and a trapezoidal rubber absorbing disk 43. The rear guide 42 is annularly arranged with a plurality of small air holes 421. The rubber absorbing disk 43 is tightly matched to the inner wall of the suction cylinder 1.
Referring to FIGS. 3 and 4, when the suction cylinder 1 absorbs air, as shown in FIG. 3, the pull 3 will pull backwards so that the piston 4 moves backwards. Since the suction cylinder 1 will induce a negative pressure, air in the vacuum will be absorbed in the suction cylinder 1. The air originally in the suction cylinder 1 and after the piston 4 will be compressed when the piston 4 moves so that the air will be drained out from the through hole 21 and the guide recess 22. On the contrary, when the pull moves forwards, the piston 4 will move forwards. Then air in front of the piston 4 will be compressed so that air passes through the rubber absorbing disk 43 (referring to FIG. 4A) and the small air hole 21 of the rear guide 42 to flow backwards until the suction cylinder 1 absorbs air again, the air is compressed again as the piston move backwards to vent out from the through hole 21 and the guide recess 22.
The prior art has the following defects,
When the pull 3 and the piston 4 moves forwards at the same time, the air in the suction cylinder 1 will be pressed and then is sprayed out from the air opening 11 to enter into a vacuum device. Since the air opening 11 has no check valve, the air original suctioned by the suction cylinder 11 will reversely return to the vacuum device after being compressed by the piston 2.
The through hole 21 and the guide recesses 22 before the handle 2 can be inserted by the pull rod, moreover, it can be used as a rear exhausting opening of the suction cylinder 1. However, the thickness of the through hole 21 and the guide recesses 22 are too thin so that the movement of the pull rod 31 and the guide piece 33 are unsteady. When they move reciprocally around the pull rod 3, they will shift or be hindered.
A front end of the handle 2 is a female screw 23 and the rear end of the suction cylinder 1 has outer thread. When the two are combined, the outer thread is screwed into the female screw 23, but in general, the screw effect is not preferred and the screw operation is not smooth.